The primary purpose of the proposed research is to investigate the long-term effects of the Communities That Care (CTC) prevention system on young adult substance use and misuse; crime, violence, and incarceration 11 and 13 years following CTC's initial installation in a randomized trial. Long-term effects of CTC will be examined also on secondary outcomes salient in young adulthood, including HIV/AIDS sexual risk behaviors; sexually transmitted infections (STIs); depression; and educational attainment. This study will be one of the first to examine the long-term effects of a community prevention system and will investigate important moderating mechanisms, including exposure to CTC and universality of CTC effects across risk- related and demographic subgroups, including Latino/a young adults. A second aim of the study is to examine the transition to adulthood among youth from small and rural towns by examining patterns in the adoption of adult roles and their associations with substance misuse and other young adult outcomes. Small communities face the unique challenge that many of their most promising young adults move away and do not contribute to the health and future of the community. Those young adults who stay may be at higher risk for many health- risking behaviors. Yet services for prevention, health care, and treatment are less available and less accessible in small and rural towns. The aims of the study will be accomplished through a 4-year continuation of the Community Youth Development Study (CYDS; PI: Hawkins, #5R01DA15183-8), a randomized trial of CTC in 24 communities across 7 states that assessed the sustainability and effects of CTC 6 to 10 years following its initial installation during the 5-year implementation phase and after technical assistance and study-provided funding ended. A panel of 5th graders (n=4407) in these communities has been surveyed annually through 12th grade. The continuation study will follow this panel into young adulthood; collecting two more waves of data at ages 21 and 23. If the study shows that CTC produces enduring improvements in outcomes that last into young adulthood, it will demonstrate CTC's lasting contribution to long-term individual and public health, which could further increase its established cost-benefit. The proposed study also has the potential to increase knowledge about the transition to adulthood and associated health-risking behaviors among youth from small towns, an understudied and underserved population. CTC could be an important tool for small and rural communities in preparing those young adults who remain in the community after high school to become productive and contributing citizens.